Perfluorocarbon (PFC) emulsions as substitutes for blood in oxygen transport are well-known. It is also well known that they should have small particle size, i.e., the perfluorocarbon should be less than 200 nanometers (0.2 micron), to enable the perfluorocarbon particles, which carry the oxygen, to pass through the smallest arteries in the body.
A problem with typical fluorocarbon emulsions is an adverse reaction that occurs when they mix with normal blood, as inevitably occurs when such emulsions are substituted for blood. It is not usually intended for such a substitution to be a complete, 100% exchange. Indeed, an absolute, 100%, exchange would be difficult to achieve even if it were intended.
The problem is that the emulsion particles tend to aggregate in the presence of blood. They do not coalesce to form a single larger particle out of several smaller ones, rather smaller particles gather together in clusters. Just like larger particles, the clusters do not pass through smaller arteries as well, which reduces oxygen transport, and they increase emulsion viscosity as well, which also impedes oxygen transport by reducing arterial flow.